The use of optical fibers has become more and more dominant in the telecommunication field. This results in a growing number of optical fibers to be handled, especially to be spliced and connected and distributed, and therefore systems for the management or organization of optical fibers are used to a growing extent. It is necessary to have an optimum organization of the fibers and furthermore the capabilities to conduct modifications and changes in a controlled manner whereby these changes should preferably be carried out so that if at all possible only those optical fibers that have to be changed and modified are moved while all other optical fibers essentially remain untouched so that undesired disturbances are avoided. This is particularly important since in the telecommunication area to a growing extent data are transmitted besides the pure transmission of voice signals, and interference with or interruption of these signals would be very disadvantageous.
These systems for the management or organization of the optical fibers are typically used in central office locations and are placed into modular optical distribution frames or racks, typically 483.6 mm (19 inch) racks.
Usually a large number of protected optical fibers enter the distribution frame or rack and have to be distributed, which can be achieved by splicing. The ends of the incoming optical fibers are spliced to individual optical fibers of a short length, the other end of which is already connected to an optical connector. The two ends are spliced together with well-known techniques and the excess length is arranged in specially designed cassettes, which typically contain a certain number of optical fibers. The further distribution is then achieved through a connection to another position in the entire distribution network through the equivalent of so-called jumper fibers.
Due to the high number of connections to be established, and the limited number of connections to be made within each cassette, it is necessary to use a large number of these cassettes. WO 95/07481 and WO 94/23324 present examples of arrays of cassettes. WO 95/07481, in particular, shows the way the fibers may be handled and distributed. Typically the cassettes are placed on rails or racks into which they are placed side by side so that they can be moved at a certain angle. This allows one to flip the cassettes like pages of a book so that any desired individual cassette can be reached in order to achieve any kinds of modifications. These can be the addition of new connections or the change of connections, a repair and the like. These systems are widely in use but it was recognized that they present some problems. For example, when choosing a certain cassette to be accessed, a high number of other cassettes must be moved, which as mentioned above results in the undesirable movement of a fairly large number of optical fibers. As also stated above, this becomes more and more critical because a pure voice signal data transmission is becoming more and more important, and bit errors are getting more and more critical. In other words, moving fibers can cause signal transmission errors.
Attempts have been made to overcome this problem, as described in WO 95/09375 and WO 95/07486. Here an arrangement is used in which the cassettes are arranged on top of each other or in a side by side arrangement, however, this is achieved so that they are fixed together through typically a common axis and the systems are designed so that an individual cassette can be moved out of the stack around the common axis so that this individual cassette becomes accessible for the above described needs. The advantage of this solution is that all fibers in the other cassettes are completely untouched and thus undisturbed. However, all of the fibers within the cassette that is moved also move, because the fibers do not pass directly by the common axis and therefore changes are unavoidable. Furthermore it is not always possible to obtain a complete access to the entire cassette in systems such as the ones described.
FR 2 789 497 shows a configuration in which the cassettes are arranged in a similar manner with a common axis, however, the cassette is provided with a curved slot, which simultaneously allows a rotation of the cassette and a longitudinal movement so that better access is obtained. This longitudinal movement depends on the specific construction and is not pre-determined. Products as described in FR 2 789 498 are believed to be available from the NEXANS Company of Bezon Cedex 95872, France.